Monday, June 17, 2013

Trying to Close Out an NBA Final Series on the Road After Winning Game 5 at Home to Go Up 3-2

With last night's Game-5 victory over the Miami Heat to take a 3-2 series lead, the San Antonio Spurs now need only a single victory to claim the NBA crown. However, Tuesday's Game 6 and (if necessary) Thursday's Game 7 will be played in Miami. Thus, the Spurs have the momentum, whereas the Heat has the home court. How much are these respective, putative advantages worth in an NBA final series?

The sample size of historical NBA finals matching the circumstances of this year's Heat-Spurs match-up is small. Still, let's take a look at similar series over the years. It should first be noted that the current 2-3-2 finals format (i.e., two games at the home of the team with the better regular-season record, the next three games at the opponent's home, and the final two back in the first city) began with the finals of the 1984-85 season. Here are the final series since then in which a team has won Game 5 (abbreviated "G5") at home to take a 3-2 lead, and then sought to win the title on the road (data from here).

As seen in the table, it's a wash: Three teams (shown in red) used their home Game-5 victory as a springboard to close out the series on the road in six games, whereas another three Game-5 winners at home (shown in blue) never got the clinching fourth win.

Two Michael Jordan-era Chicago Bulls squads entered a road Game 6 with a 3-2 lead in the finals and won the title in six, both times. However, those two experiences -- vs. Phoenix in 1992-93 and vs. Utah in 1997-98 -- are different from those in the table above. In both cases, the Bulls had led 3-1 and failed to close out the series at home in five.

We can expand the database by looking at years prior to the switch to 2-3-2, in which a 2-2-1-1-1 format (usually) was used for the finals. Under this format, a team that won Game 5 at home to go ahead 3-2 had the opportunity to wrap up the series on the road in Game 6 (although the home team for Game 5 knew that it would also play Game 7 at home, if necessary). Staying within the past 50 years, there were eight series in which a team won Game 5 at home to take a 3-2 lead and then went on the road for Game 6 (but not Game 7). They are as follows.

Again, it's a wash. Four teams (shown in dark green) won Game 5 at home to take a 3-2 lead and then captured the title on the road in Game 6. However, another four similarly situated teams (shown in orange) failed to do so.

If we assume that a road team in basketball usually has less than a 50/50 probability of winning, then the fact that a team that won Game 5 at home to take a 3-2 lead won Game 6 on the road 50% of the time in the above years suggests that there may be something to the notion of momentum in this context. There's a (somewhat) complicating factor, however. With the 2-2-1-1-1 format (prior to 1984-85), the road team in Game 6 would have been the team with the better regular-season record and thus arguably the better team. That may be why Game-5 winners may have done well in Game-6 road contests, as much or more so than benefiting from momentum.

In the 2-3-2 era, in contrast, the road team in Game 6 would be the one with the worse regular-season record. Hence, a 50% success rate for such teams in Game 6 speaks well for momentum.